Method for producing polyunsaturated fatty acid-containing composition

Abstract

Provided is a method for producing a polyunsaturated fatty acid while suppressing deterioration of a silver salt solution. A method for producing a polyunsaturated fatty acid-containing composition, the method comprising: supplying a raw material solution comprising an alkyl ester of polyunsaturated fatty acid and an aqueous solution comprising a silver salt to a flow channel mixer to contact the raw material solution with the aqueous solution; and collecting the aqueous solution comprising the silver salt which has been contacted with the raw material solution, in which the supplying the aqueous solution comprising the silver salt to the flow channel mixer and the collecting the same are performed concurrently.

The invention claimed is: 
     
       1. A method for producing a polyunsaturated fatty acid-containing composition, the method comprising:
 supplying a raw material solution comprising an alkyl ester of polyunsaturated fatty acid and an aqueous solution comprising a silver salt to a flow channel mixer to contact the raw material solution with the aqueous solution; and 
 collecting the aqueous solution comprising the silver salt which has been contacted with the raw material solution, 
 wherein the supplying of the aqueous solution comprising the silver salt to the flow channel mixer and the collecting of the aqueous solution comprising the silver salt which has been contacted with the raw material solution are performed concurrently with each other. 
 
     
     
       2. The method according to  claim 1 , further comprising:
 supplying the aqueous solution comprising the silver salt which has been collected from the flow channel mixer and an organic solvent to an extraction vessel to contact the organic solvent with the aqueous solution comprising the silver salt which has been collected from the flow channel mixer; and 
 collecting the organic solvent which has been contacted with the aqueous solution comprising the silver salt which has been collected from the flow channel mixer, 
 wherein the supplying of the aqueous solution comprising the silver salt which has been collected from the flow channel mixer to the extraction vessel and the collecting of the organic solvent which has been contacted with the aqueous solution comprising the silver salt which has been collected from the flow channel mixer are performed concurrently with each other. 
 
     
     
       3. The method according to  claim 1 , wherein the collecting of the aqueous solution comprising the silver salt which has been contacted with the raw material solution comprises collecting a mixed solution of the aqueous solution comprising the silver salt and the raw material solution from the flow channel mixer and then fractionating the aqueous solution comprising the silver salt from the collected mixed solution. 
     
     
       4. The method according to  claim 2 , wherein the collecting of the organic solvent which has been contacted with the aqueous solution comprising the silver salt comprises collecting a mixed solution of the aqueous solution comprising the silver salt and the organic solvent from the extraction vessel and then fractionating the organic solvent from the collected mixed solution. 
     
     
       5. The method according to  claim 1 , further comprising:
 supplying the raw material solution which has been collected from the flow channel mixer to a flow channel mixer again. 
 
     
     
       6. The method according to  claim 1 , wherein the supplying of the aqueous solution comprising the silver salt to the flow channel mixer, the contacting of the aqueous solution comprising the silver salt with the raw material solution, and the collecting of the aqueous solution comprising the silver salt which has been contacted with the raw material solution from the flow channel mixer are performed under hypoxic conditions. 
     
     
       7. The method according to  claim 1 , wherein a linear velocity of the aqueous solution comprising the silver salt in the flow channel mixer is 0.5 cm/sec or more. 
     
     
       8. The method according to  claim 1 , wherein the flow channel mixer has an inner diameter of 0.1 to 100 cm and a length of 0.05 to 10 m. 
     
     
       9. The method according to  claim 1 , wherein a retention time of the aqueous solution comprising the silver salt in the flow channel mixer is from 0.02 to 300 seconds. 
     
     
       10. The method according to  claim 1 , wherein a temperature of the aqueous solution comprising the silver salt upon contact with the raw material solution is from 5° C. to 30° C. 
     
     
       11. The method according to  claim 2 , wherein the extraction vessel is a flow channel mixer. 
     
     
       12. The method according to  claim 11 , wherein a linear velocity of the aqueous solution comprising the silver salt in the extraction vessel is 0.5 cm/sec or more. 
     
     
       13. The method according to  claim 11 , wherein the extraction vessel has an inner diameter of 0.1 to 100 cm and a length of 0.05 to 10 m. 
     
     
       14. The method according to  claim 11 , wherein a retention time of the aqueous solution comprising the silver salt in the extraction vessel is from 0.02 to 300 seconds. 
     
     
       15. The method according to  claim 2 , wherein a temperature of the aqueous solution comprising the silver salt upon contact with the organic solvent is from 30° C. to 80° C. 
     
     
       16. The method according to  claim 1 , wherein the raw material solution comprising an alkyl ester of polyunsaturated fatty acid has such an oxidation index that a POV is 10 or less, or AV is 0.3 or less. 
     
     
       17. The method according to  claim 1 , wherein the polyunsaturated fatty acid comprises eicosapentaenoic acid or docosahexaenoic acid. 
     
     
       18. The method according to  claim 2 , further comprising:
 supplying the raw material solution which has been collected from the flow channel mixer to a flow channel mixer again. 
 
     
     
       19. The method according to  claim 2 , wherein the supplying of the aqueous solution comprising the silver salt to the flow channel mixer, the contacting of the aqueous solution comprising the silver salt with the raw material solution, and the collecting of the aqueous solution comprising the silver salt which has been contacted with the raw material solution from the flow channel mixer are performed under hypoxic conditions. 
     
     
       20. The method according to  claim 2 , wherein a linear velocity of the aqueous solution comprising the silver salt in the flow channel mixer is 0.5 cm/sec or more. 
     
     
       21. The method according to  claim 2 , wherein the flow channel mixer has an inner diameter of 0.1 to 100 cm and a length of 0.05 to 10 m. 
     
     
       22. The method according to  claim 2 , wherein a retention time of the aqueous solution comprising the silver salt in the flow channel mixer is from 0.02 to 300 seconds. 
     
     
       23. The method according to  claim 2 , wherein a temperature of the aqueous solution comprising the silver salt upon contact with the raw material solution is from 5° C. to 30° C. 
     
     
       24. The method according to  claim 2 , wherein the raw material solution comprising an alkyl ester of polyunsaturated fatty acid has such an oxidation index that a POV is 10 or less, or AV is 0.3 or less.